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One Third of Pregnancies Come 18 Months After a Previous Birth

by Carolyn Buchanan on June 10, 2013

Carolyn Buchanan

About the Author

B.C. (before children), Carolyn was trained as a journalist — a generalist journalist. Now as a parent, she experiences news differently. What was once an item of passing interest, i.e. "Toy Train Runs on Lead Paint" or "Midnight Release Planned for Latest Power Rangers Movie" now consumes her life. Still she trains her eye to find the family relevance in everything new, and that's what she endeavors to share with you here. As a parent, and a writer for What to Expect, she will be your family-news filter (with a personal twist).

About the Blog

WhatToExpect.com supports Word of Mom as a place to share stories and highlight the many perspectives and experiences of pregnancy and parenting. However, the opinions expressed in this section are those of individual writers and do not reflect the views of Heidi Murkoff of the What to Expect brand.

It's called family planning and many couples engage in it. It includes consideration of the number of children desired and the ideal spacing between kids. Less than a year is to be avoided. Two-and-a-half to three years separation may be ideal. But the reality is that many of us aren't planning at all, and as a result, an all-too-common pregnancy interval is 18 months. According to a newly released report, one-third of U.S. pregnancies come 18 months after a previous birth.

Researchers at New York's Guttmacher Institute and the University of California looked at data from a nationally representative sample of 12,279 women from the 2006-2010 National Survey of Family Growth. They discovered that 50 percent of second pregnancies occurred within 18 to 59 months of the first; 16 percent occurred at five years or more.

Anything less than 18 months apart is considered "short birth spacing" — the assumption is that it is likely an unintended pregnancy. Women were significantly more likely to have a short "interpregnancy interval" if they were aged 15 to 19 years; married at the time of conception; or initiated childbearing after age 30 years.

For women, age 30 or older, just starting to have children, short birth spacing is usually intended. Three out of four women in this category were deliberate in having their shortly spaced pregnancies, as their fertility decreased.

Researchers focused on the question because previous studies have shown that there are health risks that can go along with short spacing between pregnancies. Risks include preeclampsia in women and low birth weight or preterm birth for the baby. As a result, unintended pregnancy can pose a public health risk and it's one that can be helped by education and improved planning.

"Pregnancy intervals of more than 18 months are considered optimal birth spacing, as recommended by the Centers for Disease Control and Prevention and others," lead researcher Laura Lindberg said in a statement. "Helping women plan and space their pregnancies through greater contraceptive access can lead to better outcomes for both mother and infant."